Safe operating area

Safe operating area

For power semiconductor device (such as BJT, MOSFET, thyristor or IGBT) a safe operating area (SOA) is defined as the voltage and current conditions over which the device can be expected to operate without self-damage.

SOA is usually presented in transistor datasheets as a graph with VCE (collector-emitter voltage) on the abscissa and ICE (collector-emitter current) on the ordinate; the safe 'area' referring to the area under the curve. The SOA specification combines the various limitations of the device — maximum voltage, current, power, junction temperature, secondary breakdown — into one curve, allowing simplified design of protection circuitry.

Often, in addition to the continuous rating, separate SOA curves are provided for short duration conditions (1 ms pulse, 10 ms pulse etc.).

SOA specifications are incredibly useful to the design engineer working on power circuits such as amplifiers and power supplies as they allow him/her to quickly determine the conditions under which a design will catch fire, allowing the design of appropriate protection circuitry and/or selection of a more capable device. SOA curves are also important in the design of foldback circuits.

The most common form of SOA protection used with BJTs senses the collector-emitter current with a low-value series resistor; the voltage across this resistor is applied to a small auxiliary transistor that progressively 'steals' base current from the power device as it passes excess collector current.

This approach is effective but not bullet-proof. In practice it is very difficult to design a protection circuit that will work under all conditions, and it is left up to the design engineer to weigh the likely fault conditions against the complexity and cost of the protection.

Types of safe operating area

* Reverse bias safe operating area (or RBSOA) is SOA when turning the device into the off-state. The RBSOA may be different from generic SOA, for example for IGBTs, upper half corner of the RBSOA is progressively cut out which reduces the RBSOA as the rate of change of the collector to emitter voltage across the device, dVce/dt, is increased.

* Forward bias safe operating area (or FBSOA) is SOA when turning the device into the on-state.

See also

* Derating


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Safe operating area — Область устойчивой работы …   Краткий толковый словарь по полиграфии

  • Area 51 — This article is about the U.S. Air Force installation in Nevada. For other uses, see Area 51 (disambiguation). Area 51 …   Wikipedia

  • Area of refuge — An Area of refuge is a location in a building designed to hold occupants during a fire or other emergency, when evacuation may not be safe or possible. Occupants can wait there until rescued by firefighters. This can apply to the following:*any… …   Wikipedia

  • Rest area — Rest stop redirects here. For the film, see Rest Stop (film). For the Stephen King story, see Rest Stop (short story). Lay by redirects here. For the form of installment purchase, see Layaway. Rest area on northbound Interstate 81 at milepost 262 …   Wikipedia

  • California Fire Safe Council — The name California Fire Safe Council (CFSC) has been used for two very different organizations. The original use of the name, from 1993 through mid 2002, referred to a loose consortium of local community based fire safe councils and other… …   Wikipedia

  • Millville Area School District — Address 330 Main Street Millville, Pennsylvania, Columbia, 17846 …   Wikipedia

  • New Safe Confinement — Computer impression of the New Safe Confinement to cover No.4 Reactor at Chernobyl The New Safe Confinement (NSC or New Shelter) is the structure intended to contain the nuclear reactor at Chernobyl, Ukraine, part of which was destroyed by the… …   Wikipedia

  • South Florida metropolitan area — South Florida redirects here. For the university in Tampa, see University of South Florida. For that school s athletic program, see South Florida Bulls. Miami–Fort Lauderdale–Pompano Beach Common name: South Florida Larg …   Wikipedia

  • Marine protected area — Milford Sound, New Zealand is a Strict Marine Reserve (Category Ia) Mitre Peak, the mountain at left, rises 1,692 m (5,551 ft) above the sea.[1] Marine protected areas, like any protected area, are regions in which human activity has… …   Wikipedia

  • Menai Bay Conservation Area — IUCN Category VI (Managed Resource Protected Area) Dolphins in the Menai Bay in Indian Ocean off Unguja coast …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”